A Manifold Absolute Pressure (MAP).
An engine knock sensor is a piezoelectric device that "listens" for abnormal vibrations or metallic pinging sounds (detonation) within your engine. When these vibrations occur, the sensor sends a signal to the Engine Control Unit (ECU), which then adjusts the ignition timing or fuel mixture to prevent damage to pistons, valves, and cylinder walls (typically P0325–P0333)
A broken knock sensor causes the engine computer (ECU) to enter safe mode, resulting in reduced power, sluggish acceleration, poor fuel economy, and a check engine light. It often causes the ignition timing to retard, preventing optimal engine performance, and should be replaced promptly to prevent severe long-term engine damage from undetected detonation